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DNA/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby Moby is looking at a hat with a magnifying glass. He sees a brown hair and picks it up. MOBY: Beep. TIM: What are you talking about? I didn't wear your hat. Moby holds up the hair accusingly MOBY: Beep. TIM: That's not my hair. Moby's chest opens up. It contains a mobile chemistry lab. He inserts the hair. After much mixing and light-flashing, the result pops up on a screen. It reads, Tim. TIM: Okay, you got me. Moby looks pleased with himself and puts the hat back on his head. Tim reads from a typed letter. TIM: Dear Tim and Moby, do all animals have DNA? From, Kevin. Yes they do, Kevin. So do all plants, fungi, algae, and bacteria. Dinosaurs and other extinct life forms had DNA, too. It's the basis for all life on Earth! An animation zooms through an array of silhouettes illustrating examples of the organisms Tim describes. The scene ends by zooming out on a rotating planet Earth. MOBY: Beep. An animation shows a spiraling strand of DNA. TIM: DNA stands for deoxyribonucleic acid. It's a complex molecule that looks kind of like a spiral staircase. This double helix shape forms into long strings. In humans and other multicellular life, DNA is unique to each individual, kind of like a fingerprint. One copy contains the complete instructions for building an organism. An animation shows a strand of DNA next to the silhouette of an adult man for scale. A ruler appears to show that it is six feet tall. TIM: It's long. Stretched all the way out, a single set of human DNA is over six feet! And there's an identical copy inside the nucleus of nearly every cell in the body. The animation zooms in on the man's silhouette until it shows a wall of cells. Each one has a strand of DNA floating inside. MOBY: Beep. TIM: Well, you can think of cells as miniature factories. But instead of cars or cell phones, these factories build proteins. That's the all-purpose construction material for life. Each individual cell turns into a mini factory, churning out little shapes that represent proteins. Inside the factory, two workers examine a blueprint that explains how create a specific protein. It shows them how to use the information stored in a strand of DNA. The workers follow the instructions and create a protein that looks just like the blueprint. TIM: Proteins can be molded to do just about anything. DNA tells your cells which proteins to build, and how to build them. It tells cells in your eyes to form out of crystallins. These transparent proteins let light shine through, so you can see. DNA tells your red blood cells to build a protein called hemoglobin. It captures oxygen as blood passes through the lungs. A series of animations illustrates how each protein works within the body, as Tim describes. TIM: Crystallins, hemoglobin, and other proteins are precision machines. They're made of hundreds, sometimes thousands, of tiny parts. If just one of those parts gets messed up, the protein may not work. MOBY: Beep. TIM: Human DNA holds instructions for building thousands of different proteins… Used in more than 200 kinds of cell... Forming dozens of different tissues… Which all come together to make you! An animation shows one small segment of DNA surrounded by illustrations of different proteins. The proteins are then replaced by illustrations of different kinds of tissue like muscle, skin and blood. Then the tissues are replaced by illustrations of specific body parts including bones, a brain, a heart, joints, muscles, and intestines. Finally, everything merges into an animation of a young girl walking down the street. TIM: All of this information is stored within an incredibly simple code. It's built into DNA's structure, in molecules we call bases. There are four different bases, and they stick together like puzzle pieces, always in the same pairs. They are cytosine, guanine, adenine, and thymine. An animation zooms in on a section of DNA, which untwists to look like a horizontal ladder. Each rung contains one base that is attached to the lower strand, and one base that is attached to the upper strand. These base pairs are highlighted as Tim names them. The illustration shows how cytosine is always paired with guanine, and adenine is always paired with thymine. TIM: You can think of bases as words in a special kind of language. They can be arranged into millions of different sequences, like sentences that spell out instructions for building any kind of protein. A section of DNA that codes for a single protein is called a gene. The DNA begins to scroll horizontally across the screen, to show how many different sequences are possible. Icons representing a skeleton, an eye, and a heart appear above the scrolling DNA. When the DNA pauses again, the eye icon clamps onto a small section. It is the gene with information about how to create an eye. TIM: The average gene is thousands of base pairs long. And humans have more than 20,000 genes! But these protein-coding sections represent only a tiny fraction of our complete DNA. The function of the rest, the non-coding DNA, is not entirely understood. The gene zigzags out to show how long it is. Then an animation of spiraling DNA shows that only a small segment is used for coding. MOBY: Beep. TIM: To fit neatly inside a cell, the DNA spiral is wound into a coil, which is wound into an even bigger coil, which is wound into a structure called a chromosome. Up close it looks like a big tangle, but it's actually precisely organized. This strong, flexible configuration keeps our personal info safe. An animation shows the DNA curling up into a chromosome, which looks like a curvy letter X. MOBY: Beep. The animation zooms out to show several chromosomes floating in a cell. They are arranged in pairs. TIM: Yeah, chromosomes come in pairs because of how we reproduce. In each of our 23 pairs, one's from the mother, and the other's from the father. Each of those is a shuffled-up version of the corresponding pair in your parents. So even though all your genes come from your parents, your chromosomes are unique. An animation shows a boy thinking about his chromosomes, which appear in a thought bubble above his head. In each pair, one is red and one is green. An image of his mother pops up with a red background, and an image of his father pops up with a green background. The color coordination shows how each parent contributes one chromosome to each pair. TIM: That's why family members tend to look similar, but have lots of differences, too. Eye color, hair type, and facial features are genetic traits. You inherit them in the genes you get from your parents. An animation shows the boy along with the rest of his family. Each one of the children has a few has a few features from each parent, like hair color, eye shape, and glasses. MOBY: Beep. TIM: The number of chromosomes differs by species, kinda randomly. Humans have 46; lobsters have 100; corn has 20. A human, a lobster, and an ear of corn appear on pedestals arranged by number of chromosomes. Then the human becomes a silhouette with its arms and legs spread, surrounded by diagram lines. TIM: Researchers have mapped the human genome, the complete sequence for human DNA. Comparing our genes to those of other life forms, we've discovered a lot in common. Humans share 96 percent of the same genes as chimpanzees, which isn't too surprising. But we also share 85 percent with mice… 60 percent with fruit flies… and 50 percent with bananas. The human silhouette leaps forward and becomes a chimpanzee in front of a pie chart. The chart illustrates the ratio of genes humans and chimps share. The animal and chart adjust as Tim describes. MOBY: Beep. Moby has just bitten into a banana. He spits it out and looks concerned. TIM: We even have genes in common with bacteria and other single-celled life! An animation shows silhouettes of bacteria and other single-celled organisms TIM: This supports what Charles Darwin proposed in his theory of evolution more than 150 years ago: All life on Earth is connected, and likely traces back to a single ancestor. An animation shows planet Earth surrounded by images of a human, a banana, a fly, mice, a chimp, and bacteria. A line connects the images to illustrate how they all share a common ancestor. Then the Earth morphs into a single-celled organism to illustrate the earliest life form. MOBY: Beep. TIM: Yeah, some of the technology to come out of all this is pretty crazy. Like gene therapy, manipulating our DNA to cure diseases. That can mean turning a defective gene off… Swapping a healthy gene in its place… Or adding entirely new genes into our DNA. An animation shows a horizontal strand of DNA with a ragged-looking gene. The gene turns gray and then is replaced by a healthy version. Then a new gene is inserted. TIM: Scientists have been doing that for decades with crops. They can insert specific genes into plants to get better traits, like, bigger apples, or tomatoes that can grow in colder weather. The results are called genetically modified organisms, or GMOs. Some worry about damage they might cause to the environment. An animation shows a farm. The silhouette of an apple tree appears and the apples balloon in size as Tim describes. They fall from the tree and a girl picks one up and starts tossing it in the air. Then pollen blows off the tree into another yard that a man is mowing. As the man mows, silhouettes of monstrous trees begin to crop up around him. MOBY: Beep. TIM: Like, if GMO crops cross-bred with plants in nearby fields. That could have unpredictable results. Gene therapy may carry similar risks to our own health. There's still so much we don't understand about DNA. So we need to be careful with these new technologies. Tim picks a blond hair off Moby's shoulder. TIM: Hey, let's see who this curly blond hair belongs to! Moby takes the hair and inserts it into his lab. It swishes and beeps. The result reads, Tim. Tim frowns. TIM: It's gonna say Tim every time, isn't it? Moby hangs his head. MOBY: Beep. Category:BrainPOP Transcripts Category:BrainPOP Science Transcripts Category:BrainPOP Health Transcripts